THE PURPLE EMPEROR. 57 



Plate 31, the under side of this butterfly is exceedingly pretty. 

 On the same plate there is a figure of the rare variety known 

 as iole (for the loan of which I am indebted to Mr. Sabine), in 

 which most of the white spots are absent or obscured. Inter- 

 mediates between this extreme form and the type also occur, 

 but all such aberrations are uncommon. 



The egg (Plate 28) may be looked for in August on the 

 upper surface of a leaf of the sallow (Salix caftrea). According 

 to Buckler, it is pale olive green in colour, and cylindrical in 

 shape ; the height from base to top being about equal to the 

 width through from side to side. It has about fourteen ribs. 



The caterpillar in October, just before hibernation, is dingy 

 green roughened with numerous whitish warts from which 

 arise short bristles, some of the latter appearing to be tinged 

 with reddish, and those along the sides longer than those on 

 the upper part of the body ; the straight lines along the 

 back and the oblique ones on the sides are yellowish. The. 

 head and the two horn-like projections, reminding one of the 

 horns of a slug, are reddish-grey and covered with warts and 

 bristles. The anal points (tails), which lie close together, are 

 tipped with reddish. It should be mentioned here that on 

 emerging from the egg the young caterpillar is without horns ; 

 these are not developed until the first skin is thrown off, which 

 event happens from eight to twelve days after hatching. 



The full-grown caterpillar is green, merging into yellowish 

 towards the anal points (tails) ; the oblique stripes on the 

 sides are yellowish, edged with reddish. The individual 

 depicted on the plate took up a position for change to the 

 chrysalis on June 6. It spun a mat of silk to the under side 

 of a sallow leaf, and the next day it was found suspended 

 by the claspers, which were grasping the silken mat. On 

 the fourth day the chrysalis was fully developed, and from 

 this a male butterfly emerged on June 24, an unusually early 

 date. 



